- buttons: code tweaks
- buttons: Fix dynamic buttons not showing after they are hidden, use our own table for storing button parents, fix a rare bug where a button would hide if it was changed from from "hover" to "show" whilst it was fading out.
- buttons: shouldn't need these :Show calls anymore.
- buttons: Instead of trying to force our buttons to stay hidden by messing with the Hide/Show funcs, create a hidden frame and simply re-parent the buttons to that frame. That way other addons can call :Show until the cows come home, the button will not show, and we don't taint the hide/show funcs. Also remove some old DB cleanup code.